Reference electrode catheters for measuring various bodily fluids are well known. These catheters typically include an Ag/AgCl (silver/silver chloride) electrode wire in a compartment filled with a KCl (potassium chloride) solution. The compartment communicates with its outer surroundings by means of a porous plug creating a liquid junction. Said reference electrode catheters can be used as an exploring electrode catheter in potential difference measurement. Other reference electrodes that have been used as exploring electrodes in intragastrointestinal potential difference measurements have included half cells and salt bridges communicating with conducting perfusate in a lumen of a catheter.
Electrical potential difference is the voltage difference between two non-polarizable electrodes on either side of a membrane after elimination of junction potentials (see Hojgard 1991). Because there is little difference in potential between blood in the periphery and the gastrointestinal serosal surface, gastrointestinal transmucosal electrical potential difference is the potential between an intragastrointestinal exploring electrode and an electrically adjacent intravenous reference electrode. An intravenous reference electrode can be an Ag/AgCl reference electrode catheter placed in a saline intravenous infusion line.
A 24 hour pH and potential difference data logger, the Proxima Light, by Synectics Medical, Inc., 1425 Greenway Drive, Suite 600, Irving, Tex. 75038, was described by Scarpignato and Galmiche 1990.
Pressures measured with intragastrointestinal catheters are also well known. Pressure catheters exist where sterile water is perfused by means of a perfusion pump through a lumen in the catheter and out through an opening at the site (often at the distal end of the catheter) where pressure is to be measured. If the pressure changes at said measuring site, a pressure transducer at the proximal end of the catheter will measure the pressure change.
The present invention is a new design for a saline perfused exploring electrode catheter where the exploring Ag/AgCl electrode is directly inserted into the perfusate in a lumen for the measurement of electrical potential difference, while simultaneously using said perfusate for measuring pressure at the same site. The two parameters, potential difference and pressure, are measured simultaneously at the same point and with one measurement lumen only. In this way, two parameters can be measured by the same perfused catheter. In addition, no expensive bridge connection is needed for the exploring electrode.